Colour photography



United States Patent Or ice 3,114,634 QQLGUR Pli lllilGRAhHY .lehn liernard Erewn, Swluton, and Douglas William Stamrners, Epping, England, assignors to lliord Limlied. lilo-rd, 1.. land, a British company No Drawing. Filed Get. 2.4, 196i, der- No. M7 ,185

Claims priority, application Great Britain Get. 27, race 6 Qlaims. (Cl. 96-26) This invention relates to colour photography and particularly to the silver-dye-bleach process of colour photography.

In this process a photographic silver halide emulsion layer, usually a gelatino silver halide emulsion layer, includes as a uniiorm dispersion therein, a suitable dyestutl. A latent silver image is formed in the layer and is developed to a silver image. The layer is then treated with a bleach bath which has the effect of oxidising the silver image and simultaneously reducing (bleaching) the dyestuii in the region of the silver image. The silver salts and any residual silver are then removed and the layer then contains only a dyestuli image which is complementary in sign to the original silver image.

ddl hdd l Patented Dec. l7, 1953 ensure that the dyestuff employed will not diffuse from the gelatin emulsion layer in which it is incorporated, and various proposals, such as mordanting, have been made to overcome this difficulty. In selecting dyestuffs 5 for use, moreover, it is desirable that they should be bleached rapidly by the bleaching baths employed and also important that their inclusion in the emulsion layer should not too seriously reduce the sensitivity of the emulsion. In addition, of course, it is desirable that the dye 0 should approach as closely as possible to the theoretical requirement that, of red, blue and green light, it should absorb all of one while fully transmitting or reflecting both of the others.

It is an object of the present invention to provide a class of yellow dyestulis for use in the silver-dye-bleach process which closely approach the desiderata set forth above.

According to the present invention a process for the production or" a yellow dyestu'ff image in a photographic layer comprises including in a light-sensitive gelatino silver halide emulsion layer, or in a plain gelatin layer coated adjacent thereto, a yellow dyestufi of the formula:

Variations are possible in this process. For example, the layer may be dyed with the dyestuff alter the exposure step or alter the development of the silver image, or the dyestufi may be included in a plain gelatin layer coated adjacent to the emulsion layer. A large number of patents have been granted in respect to the process, the main details of which can be ascertained from British patent specifications Nos. 397,159 and 397,188.

In order to produce a record in full colour there is generally employed a multilayer material which contains three light-sensitive silver halide emulsion layers, one sensitive to blue light only and the other sensitised to green and red light respectively. To prevent these latter layers from recording blue light in addition to the light to which they are sensitised, it is usual to provide a blueabsorbing filter layer between these latter layers and the emulsion which is sensitive only to blue, a common form of assembly being:

(a) support layer (b) red-sensitive emulsion layer (c) green-sensitive emulsion layer (0!) blue-absorbing filter layer (e) blue-sensitive emulsion layer.

Layer (0!) is not always essential since layer (e), when dyed yellow, may provide a suilicient barrier to blue light. l olychromatic light incident on layer (:2) causes the formation of latent silver images in layers (e), (c) and (b) respectively recording in those layers the blue, green and red sensations of the exposing light.

in the silver-dye-bleach process as ordinarily practised, layer (19) is dyed blue-green (cyan), layer (0) is dyed magenta and layer (e) is dyed yellow. Accordingly, when the material is exposed, developed to form silver images and subjected to the required bleaching treatment and treated to remove residual silver salts and silver, the final product carries positive yellow, magenta and cyan images complementary to the negative silver images formed on development, so that when viewed it provides an accurate representation of the original subject of the exposure.

A principal di'iiiculty associated with the process is to wherein R represents hydrogen, methyl or halogen, and

X represents a covalent single bond or a -CH group,

forming a latent silver image in said layer, developing said image, subjecting the developed image to treatment which bleaches or removes the silver image and simultaneously bleaches the dyesturi in situ therewith, and

removing any residual silver and silver salts from the product.

The aforesaid dyestuffs may be obtained by the general 40 technique of coupling a compound of the general formula:

N Hz with 2,5-dichlorosulphanilic acid.

DYESTUFF A 24.2 parts of 2:5-dichlorsulphanilic acid is added to 400 parts or water followed by 9.45 parts of hydrochloric acid (27%) and the mixture stirred for 30 minutes. Sodium nitrite (7.0 parts) is then added as fast as it is absorbed at 18-20" C. Diazotisation is regarded as complete when an excess of nitrous acid is demonstrable fifteen minutes after the last addition of sodium nitrite. The excess nitrous acid is destroyed by the addition of sulphamic acid.

18.6 parts of 4:4-bis(5"-arnino-3-methyl-l-pyrazo lyl) -3:3'-dimethyldiphenyl is added to 200 parts of water followed by 15 parts of hydrochloric acid (27%) and thc mixture stirred until a clear solution is obtained. Thi

5 solution is then added to the diazo suspension and th mixture stirred for two hours. Coupling proceeds onl part way under these conditions. Sodium carbonat (18.55 parts) dissolved in 175 parts of water is adde dropwise over two hours and the mixture stirred for l hours. t

The yellow dyestuti is filtered oil and dried.

The required intermediate bis-pyrazole may be pr 3 pared by condensation of 4:4'-dihydrazino-3:3'-dimethyldiphenyl (Annalen, 352, 116 (1907) with 1-cyano-2- iminopropane in the following way:

79 parts of 4:4'dihydrazino-3:3'-dimethyldiphenyl dihydrochloride is slurried with 1400 parts of cold water.

It is then allowed to cool to below 50 C. and filtered. The resulting paste is washed with water until the washings are free of alkali, drained as dry as possible and dried.

DYESTUFF B 12.1 parts of 2:5-dichlorosulphanilic acid is stirred with a mixture of 8.7 parts of 32% hydrochloric acid The mixture is diluted with 390 parts of water and diazotised by adding a solution of 3.45 parts of sodium most neutralised to Congo red test paper with sodium ture at a pH value of 2.0-2.1 units. 93 parts of common salt is added and allowed to dissolve. A solution of 4.24 parts of sodium carbonate in 40 parts of water is added evenly over 1 /22 hours which raises the pH value of the coupling to 6.5-7.0 units. The mixture is stirred for a further 18 hours at room temperature.

The yellow dye is filtered off, washed on the filter with potassium acetate 25% solution until free from chloride ion, then washed with methylated spirits and finally dried in an oven. There results 24.4 parts of dye.

The 4 4-bis 5 "amino-3 methyl-1"-pyrazolyl)-diphenyl used in the above preparation may be made as follows:

274 parts of benzidine hydrochloride (equivalent to 0.74 mol) is slurried with 370 parts of Water for 15 minutes. 215 parts 32% hydrochloric acid and 2590 parts of water are added. The suspension is cooled to C. by adding 185 parts of ice and the suspension tetrazotised by adding a solution of 102 parts of sodium nitrite dissolved in 696 parts of water, maintaining the temperature at below C. Tetrazotisation is complete when excess nitrous acid is still detectable minutes after the last addition of sodium nitrite solution. The tetrazotisation utes to a stirred mixture of 836 parts of stannous chloride crystals and 740 parts 36% hydrochloric acid at below 5 C. After stirring for a further hour at below 5 C. the mixture is heated to C. and stirred for 1 hour at 50 C. The mixture is cooled to below 25 C. and the precipitate of 4:4'-dihydrazino diphenyl dihydrochloride filtered off. The filter cake is washed with 12% hydro- :hloric acid to remove tin compounds. Thus there is ibtained 715 parts of 4:4'-dihydrazino diphenyl dihydrozhloride paste equivalent to 122 parts at 100%.

24.8 parts of I-cyano-2-iminopropane is stirred with 93 parts of water and 46 parts of 36% hydrochloric acid t room temperature for 1 /2 hours. 458 parts equivalent 78.2 parts 100% of 4:4-dihydrazino diphenyl dihydrohloride is added to the stirred mixture and the mixture is heated to the boil, and boiled for 3 hours maintaining the volume constant by adding Water as required. The

The cooled filtrates and washes are added to 386 parts of 32% sodium hydroxide liquor and the mixture boiled for 3 hours. The cooled mixture is filtered, washed alkali free with cold water and dried to give 67.4 parts of crude product. The crude product is puri- The product 18 further purified by dissolving in 520 parts 7.3% hydrochloric acid at the boil, filtering, and the hydrochloride which crystallises on cooling is filtered off. The hydro- DYESTUFF C Procedure exactly as for Dyestutf B except that 8.95 parts of 4:4'-bis(5"amino-3"methyl-1"pyrazolyDdiphenylmethane is used instead of the 4:4'-bis(5"amino-3- methyl-1"-pyrazolyl)-diphenyl. There results 24.3 parts of dye.

The 4 4'-bis 5 "amino-3 "methyl-1"-pyrazolyl)diphenylmethane used in the above preparation may be made as follows:

A mixture of 9.9 parts 4:4'-diaminodiphenylmethane, 200 parts Water and 29 parts 32% hydrochloric acid is cooled to 0 C. by adding 12.5 parts of ice and tetrazotised at below 5 C. by adding a solution of 6.9 parts of sodium nitrite in 50 parts of water. The filtered tetrazotisation solution is added over 15-20 minutes to a stirred mixture of 56.4 parts of stannous chloride crystals, 50 parts of 36% hydrochloric acid and 50 parts of ice at below 5 C. The mixture is stirred for a further 1 hour at below 5 C. and then for 1 hour at C. The solution is treated with 1 part of active carbon and filtered at 85 C. The cooled solution is treated with 590 parts of 36% hydrochloric acid, the precipitate filtered off and washed with 12% hydrochloric acid to remove tin compounds. Thus there is obtained 23.9 parts of 4:4'-dihydrazino diphenyl methane dihydrochloride paste equivalent to 10.6 parts at 36.1 parts of 1-cyano-2-iminopropane is stirred with a mixture of 59.5 parts of 36% hydrochloric acid and 250 parts of water for 1 /2 hours at room temperature. 135 parts of 4:4-dihydrazino diphenylmethane dihydrochlofiltered at 60-70 C. The residue is washed with a little hot water. The combined filtrate and washes are treated with 520 parts of 16% sodium hydroxide liquor at the boil for 3 hours. The mixture is cooled to 60 C., filtered, the residue washed alkali free with water and dried. There results 64.7 parts of crude 4:4-bis(5"amino-3methyl-1"-pyrazolyl)diphenylmethane. fied by extraction with 260 parts of boiling toluene, filtered hot and washed with parts of cold toluene. The purifiti product is dried to give 57.9 parts, M.P. 200- 202 DYESTUFF D Procedure exactly as for Dyestuif B except that 10.4 parts of 4:4-bis(5"amino-3"methyl-l" pyrazolyl)3:3 dichloro diphenyl is used instead of the 4:4-bis(5amino- 3"methyl-1" pyrazolyDdiphenyl. There results 25.9 parts of dye.

The 4:4-bis(5"amino-3"methyl-1" pyrazolyl)3:3" dichloro diphenyl used in the above preparation may be made as follows:

A mixture of 40 parts of 3:3 dichlorobenzidinesulphate (0.09 mol), 400 parts of water, 58 parts 32% hydrochloric acid and 25 parts of ice is tetrazotised at below C. by adding a solution of 12.4 parts of sodium nitrite in 90 parts of water. The filtered tetrazotisation solution is added over -20 minutes to a stirred mixture of 112.8 parts of stannous chloride crystals and 100 parts of 36% hydrochloric acid at below 5 C. After stirring for a further one hour at below 5 C. the mixture is stirred for 1 hour at 85 C. The mixture is cooled to room temperature, filtered and washed with 12% hydrochloric acid to remove tin compounds. The crude 3:3'-dichloro 4:4'-dihydrazino diphenyl dihydrochloride is purified by recrystallisation from water to give 65 parts paste product equivalent to 14.8 parts at 100%.

12.5 parts of 1-cyano2-iminopropane is st rred with a mixture of 90 parts of water and 20.3 parts of 36% hydrochloric acid at room temperature for 1 /2 hours. 65 parts of 3a3-dichloro-4:4-dihydrazino-diphenyl dihydrochloride paste equivalent to 14.8 parts at 160% is added and the mixture boiled for 3 hours maintaining the volume constant by adding water as required. The mixture is treated with 1.75 parts of active carbon and filtered at 60 C. and the residue washed with a little hot water. The combined filtrate and Washes are treated with 200 parts of 16% sodium hydroxide liquor at the boil for 3 hours. The mixture is cooled to below C., filtered, washed alkali free with water and dried. There results 27 parts of crude 4z4-bis(5amino-3methyl-1 pyrazolyl)3 :3'-dichlorodiphenyl which is purified by extraction with 173 parts of boiling toluene. The product is filtered oil hot, washed with a little toluene and dried. There results 26.2 parts of purified product, Ml. 256-257 C.

Further, according to the invention a process of colour photography comprises a process as just set forth in which the gelatino silver halide layer is blue-sensitive and constitutes one of the layers of a multilayer photographic material which further contains photographic emulsion layers sensitive to green and red light and respectively dyed with magenta and cyan dyestuffs, and the said yellow dyestuil is included in said blue-sensitive layer or in a plain gelatin layer coated adjacent thereto. More particularly the invention provides a process in which the said yellow dyed layer is layer (e) of an assembly consisting oi:

(a) support layer (b) red-sensitive emulsion layer dyed cyan (c) green-sensitive emulsion layer dyed magenta (d) blue-absorbing filter layer (e) blue-sensitive emulsion layer dyed yellow, optionally with plain colloid separating layers between some or all of the adjacent layers recited.

The invention further includes such light-sensitive materials employed in the aforesaid processes, and suitable for variants of those processes, which consist of or include a gelatino silver halide emulsion layer containing a yellow dyestufi? as above set forth.

The bleaching of the yellow dyestuffs employed in this invention can be effected by any of the types of bleaching bath commonly employed in the silver-dye-bleach process.

The plain use of acid, e.g. hydrobromic or hydrochloric, is efiective but is very slow. The inclusion of halide salts has an accelerative effect, but these bleaching baths are still slow. The inclusion of a solvent for silver halide such as thiourea or pyridine has a strongly accelerative eilect, and this can be greatly increased by the inclusion of an accelerating substance or catalyst. In these connections reference may be made to British patent specifications Nos. 397,159 and 490,451 for suitable bleaching baths.

The following examples, which for simplicity are concerned only with the treatment of a single layer containing the yellow dyestuii, will serve to illustrate the invention:

ture of 3 parts n-propanol and 19 parts water.

Example 1 1.92 grns. of the yellow Dyestuff A prepared as described above are dissolved in 192 mls. of a mixture of 10 parts n-propanol and parts water. This solution is added to 608 mls. of a silver chlorobrornide emulsion containing 2.18 gms. silver as silver halide. The mixfilm to give a coating weight of 4.2 mgms. of silver (as silver halide) per square decimetre.

The dried coating is exposed to light to record an image therein and processed at 68 F. as follows:

(1) Develop to a silver image by two minutes treatment in the following developer:

Gms. Metol 0.75 Sodium sulphite (cryst.) 25 Hydroquinone 3 Sodium carbonate (cryst.) 40 Potassium bromide 1 Water to 1 litre.

(2) Rinse 30 seconds.

(3) Fix in 20% sodium thiosulphate for 3 minutes.

(4) Rinse 30 seconds.

(5) Harden in 4% formalin.

(6) Wash 10 minutes.

(7) Dye-bleach for 8 minutes in the following bath:

Hydrochloric acid (8.6. 1.19) ccs 100 Potassium bromide gms 12.5 Thiourea gms l0 2:3-dimethyl quinoxaline gms 0.1 Water to 1 litre.

(8) Wash 5 minutes.

(9) Silver-bleach for 5 minutes in the following bath:

Copper sulphate (cryst.) gms 16% Sodium chloride gms 100 Hydrochloric acid (conc.) -ccs 50 Water to 1 litre.

(10) Wash 5 minutes.

(11) Fix in 20% sodium thiosulphate for 3 minutes. (12) Wash for 10 minutes and dry.

A reverse image in yellow dye is obtained. Steps 4 and 5 may be omitted if the original emulsion 1S hardened or provided with a hardened gelatin supercoat.

Example 2 2 g. of Dyestuif B are dissolved in 200 ml. of a mix- This 600 ml. of a silver chlorobromide emulsion containing 2.7 g. silver (as silver halide). The mixture is coated on film to give a coating weight of 5.2 mg. of silver (as silver halide) per square decimetre.

The dried coating is exposed to light to record an image therein and processed at 68 F. as in Example 1.

solution is added to Example 3 2 g. of Dyestuif C are dissolved in 200 ml. of a mixture of 24 parts n-propanol and 106 parts of water. This solution is added to 600 ml. of a silver chlorobrornide emulsion containing 2.15 g. silver as silver halide. The mixture is coated on film to give a coating weight 01 4.2 mg. of silver (as silver halide) per square decimetre The dried coating is exposed to light to record an imagt therein and processed at 68 F. as in Example 1.

Example 4 2 g. of Dyestuff D are dissolved in 200 ml. of a mi) ture of 35 parts n-propanol and parts of water. Th solution is added to 600 ml. of a silver chlorobromic' emulsion containing 3.25 g. silver as silver halide. Tl mixture is coated on film to give a coating weight 1 6.3 mg. silver (as silver halide) per square decimetre.

The dried coating is exposed to light to record an ima; therein and processed at 68 F. as in Example 1.

Similar results are obtained using the other dyestuffs falling within the formula first set forth herein.

When the process is repeated with a gelatin coating containing dye but not silver halide, it is found that substantially the same density of dye can be measured after processing as before.

All the said dyestuffs have good resistance to migration, bleach rapidly and effectively and are much supehitherto employed for the purpose.

What we claim is: 1. A process for the production of a yellow dyestufi (In Ho3s- -N=N bH I i image in a photographic element which comprises forn ing a latent silver image in a light-sensitive gelatino silver halide emulsion layer of said element, which layer has in coactive relation thereto a yellow dyestuif of the formula:

wherein R is selected from the group consisting of hydrogen, methyl and halogen, and X represents a linkage selected from the group consisting of a covalent single bond and a CH group, developing said image, substuif in situ therewith, and removing any residual silver and silver salts from the product.

2. A process according to claim 1 wherein the gelatino silver halide layer 1s blue-sensitive and constitutes one 45 3. A process according to claim 1 wherein said photographic element comprises the following layers in order:

(a) support layer (/2) red-sensitive emulsion layer dyed cyan 55 (c) green-sensitive emulsion layer dyed magenta (d) blue-absorbing filter layer (e) blue-sensitive emulsion layer dyed yellow with a yellow dyestuff of the said formula.

4. A photographic element comprising a gelatino silver halide emulsion layer containing a yellow dyestulf of the formula:

('11 NH wherein R is selected from the group consisting of hydrogen, methyl and halogen, and X represents a linkage selected from the group consisting of a covalent single bond and a CH group.

5. A multilayer photographic material which comprises gelatino silver halide emulsion layers respectively sensi- NH wherein R is selected from the group consisting of hydrogen, methyl and halogen, and X represents a linkage selected from the group consisting of a covalent single bond and a CH group.

6. A multilayer photographic material according to References Cited in the file of this patent UNITED STATES PATENTS 2,612,448 Gaspar et al Sept. 30, 1952 2,694,636 Keller Nov. 16, 1954 3,038,802 Keller et al June 12, 1962 FOREIGN PATENTS 885,851 France Sept. 28, 1943 841,300 Great Britain July 13, 1960 OTHER REFERENCES Cornwell-Clyne: Colour Cinematography, published by Chapman and Hall, Ltd., London, 1951, 3rd edition, pp. 4l9-42l relied on. 

1. A PROCESS FOR THE PRODUCTION OF A YELLOW DYESTUFF IMAGE IN A PHOTOGRAPHIC ELEMENT WHICH COMPRISES FORMING A LATENT SILVER IMAGE IN A LIGHT-SENSITIVE GELATINO SILVER HALIDE EMULSION LAYER OF SAID ELEMENT, WHICH LAYER HAS IN COACTIVE RELATION THERETO A YELLOW DYESTUFF OF THE FORMULA: 